Mobile Sensing of Spatial Fields: Challenges and Opportunities

Sensing of spatial fields is traditionally studied in a setting where static sensors scattered around space take measurements of the spatial field at their locations. In recent years mobile sensors have been employed in numerous applications for measuring spatio-temporal fields as they move through space. In this talk, we study this emerging paradigm of mobile sensing focussing on the following specific problems:

(1) Designing efficient trajectories for mobile sensors: We introduce the notion of path density, defined as the total distance traveled by the mobile sensors per unit area, and obtain fundamental limits on the path density of mobile sensor trajectories that admit stable sampling of a bandlimited spatial field. These results generalize Landau's bounds on sampling density for classical sampling.

(2) Spatial anti-aliasing: We show that mobile sensing can be used to perform anti-aliasing filtering of spatial fields, which is impossible in static sensing. We quantify the improvement over static sensing in terms of suppressing out-of-band noise.

(3) Privacy of mobility traces: Recent work has shown that users can be identified from anonymized mobile traces using auxiliary information about their locations. We study the problem of deanonymizing time-averaged statistics of mobile traces. We show that an attacker who has observed some users' locations over a time period, can match their trajectories to the correct statistics with high accuracy. Studying the matching problem as a hypothesis testing problem, we identify the asymptotically optimal matching scheme that can be employed by the attacker. These results further highlight the privacy concerns in collecting location information in citizen sensing schemes.
Jayakrishnan Unnikrishnan is a postdoctoral researcher at the Audiovisual Communications laboratory, Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland. He received his Ph.D. degree in electrical and computer engineering from the University of Illinois at Urbana-Champaign in 2010. His main research interests are in signal processing, information privacy, detection and estimation theory and wireless communications. Prior to joining University of Illinois, he completed his B. Tech. degree in electrical engineering from the Indian Institute of Technology Madras, Chennai, India in 2005.

Dr. Unnikrishnan is a recipient of the Vodafone Graduate Fellowship Award from the University of Illinois at Urbana-Champaign for 2007-2008 and the E. A. Reid Fellowship Award from the ECE department at the University of Illinois at Urbana-Champaign for 2010-2011.